My eight year old would like to know if it happened, how long would it take the moon to fall to earth?

Question

In theory how fast would an object of that size fall to earth taking into account its weight / density and our gravity

Answer 1

Strangly enough it is already happening,,,,but not to worry the moon only gets closer to the earth by about a millimeter a year,,,but the length of time would all depend on the speed,,,very very fast,,just a day,,,,very slowly would take longer

Answer 2

First, the moon would have to magically stop moving in its orbit. Then it would fall to the Earth.

I get something about 4 days 12 hours, using the formula:

T[f f] = pi R^(3/2) / (2 *sqrt( 2 GM ))
with R = 385,000,000 distance to Moon, meters
G = 6.6743E-11 Gravitational constant
M = 6.9712E+24 Mass of Earth + Moon, in kg
T[ f f] = 389,000 seconds = 4.502 days.

The final speed at impact would be about 43,400 km / hr (27,000 miles per hour). The Apollo 10 crew set a speed record of 24,790 mph, on 26 May 1969 -- but they were a LOT smaller than the Moon!

That's not the exact formula, but it's close enough. An exact formula would have to include the fact that the Earth and Moon have definite sizes -- they are not points in space.

Answer 3

The moon IS falling toward the earth. Its happening as i write this. The cause is gravity. Since the distance from earth to moon is approx. 250,000 miles and it circles the earth once every 28 days, it travels that distance in about 14 days. If my math is right, or at least right enough for practical purposes, the moon falls toward the earth at about 744 miles per hour. The problem, thank the gods, is that when the moon gets to where we were, we aren't there any more. We're moving too. Its called being in orbit. The moon has been in that condition for about 4 billion years. Its not going to change, although distances have varied over time.

Answer 4

The moon is held in place by opposing forces: the earths gravitational force (pulling it toward earth) and centrifical force (spinning around the earth). As long as the moon keep spinning and the earth keeps pulling it will not fall. If for instance the moon stopped spining around the earth. It would simply be acted upon by gravity. The time it took to fall to earth would be a function of gravity and mass. Probably about a day.

Answer 5

If the Moon were somehow stopped still in it's orbit, I think it would take about a week to fall to Earth. The Apollo space craft took about 3 days to get back to Earth, and they were basically "falling" all the way, but they started with a speed of a few thousand miles per hour, not from zero speed.

Answer 6

Its going the wrong way to fall to earth. It is getting farther away. About a half inch a year. in a hundred years it will be fifty inches farther away. about four feet. the Apollo astronauts placed a mirror on the moon in 1969 and a Lazar tracks the movement.

If it were to FALL that's 32ft per sec / per sec at 239,000 miles. that's 5280 ft per mile at 32 ft the first sec 64ft the second etc doing the math, that's:

239,000 X 5280= 1.2 billion or so. every second the speed doubles calc 5000 min 188 hours
or 7.8 days... the moon effects tides though so we would all drown first....

PS: The Earth is moving to so where in the moons orbit did it start to fall? Lots of varyables here.
did it start to fall when it was in front of us moving around the sun or behind us> it is falling and we are gone before it gets here so the answer is NEVER

Answer 7

This is purely hypothesis, but 3.666666hours.
The moon is approximately 242,000 miles from Earth. The moon and the earth travel together around the sun. The orbital speed is approximately 66,000 miles per hour.
If the moon was to suddenly fall to earth at these distances and speeds it would take 3.666666 hours (3 hrs. 40 mins.).

It would make a 'BIG BANG!!!!' and I don't think we would wake up from it.

Wonderful how a child's mind works GREAT!!!!!

Answer 8

That depends on how fast it fell. The moon is about 250,000 miles from Earth. At a speed of 1,000 mph it would take about 250 hours which is about 10 and a half days.

Answer 9

I dont know exactly too many variables...on Apollo 13 they calculated that it would take about 4 days for the spacecraft to reach the earth on a free return trajectory...bearing in mind the extra mass of the moon I should think it would take less than that....good question though...nice to have something intelligent on here.

Answer 10

this is the PERFECT opportunity to spend some time with him. Get him a book on space and the moon. I know it's something like ***million miles away (there is an exact measurement somewhere in the WWW. ) If budget allows why not get a telescope from walmart probably only around 50$ or so.

Answer 11

well a hard one to answer you would need to know mass weight of the moon + speed and then acceleration with the pull of the gravity as the moon got closer

regards x kitti x